Hello Wayne,

Thanks for reaching out to Ask Extension with your questions about Japanese Beetles. 

Japanese Beetles are very mobile, so just because you saw adults in your yard last season does not necessarily mean that they laid eggs and overwintered in your lawn. Have you noticed any lawn damage last August through September, or so far this season? If not, you likely don't need to worry about it.

These beetles have a 1-year life cycle, and adult beetles emerge in early summer and are gone by August usually, although sometimes you will still see the adults into September. The rest of the time they are in their larval stages in the soil. Most homeowner lawns are not kept moist enough for the beetle larvae to survive their early stage(s). One of the best ways to deter them from reproducing in your lawn is to cut back the water to your lawn in July and August. 

I would first check to see if you have any grubs in your lawn if you do see damaged areas. There are many other types of grubs that live in our lawns, so when people do find grubs, they aren't necessarily going to be JB. If you wish to still treat your lawn with a pesticide, then timing is key and you must read and follow the label in it's entirety, as the label is the law. Right now, the adults are emerging, so it is too late. You will want to treat when they are laying their eggs (July-August). 

Here is more information about JB and how to control them with different methods:

 https://extension.colostate.edu/topic-areas/insects/japanese-beetle-5-601/

I hope this helps!

 Dawn Fradkin